Pneumatic two-position controller

ABSTRACT

A pneumatic two-position controller in which the control point is adjusted pneumatically by means of a pressure distributor network connected between one output of a differential pressure amplifier and a source of auxiliary pressure, the pressure distributor network providing the control point pressure to one input of the differential pressure amplifier.

United States Patent 1 1 1 1 52,193

Bader Aug. 14, 1973 [54] PNEUMATIC TWO-POSITION 3,540,478 11/1970 116l37/625.5 CONTROLLER 3,168,898 2/1965 Samet.... 235/201 ME 3,070,29512/1962 Gi8tlii.... 235/201 ME Inventor: Horst Baden Stuttgart, Ge any3,303,999 2/1967 Mamy 235/201 ME 3,311,301 3/1967 Chabrieret 61..235/201 ME [73] Assgnee' 3,319,885 5/1967 Eige 235/201 ME Gemany3,612,085 10/1971 Clark 137/815 x 22 Filed; Man 5 1971 3,613,708 10/l97lKampe et al 137/815 [211 128063 Primary ExaminerSamuel ScottAttorney-Craig, Antonelli, Stewart & Hill [30] Foreign ApplicationPriority Data Mar. 25, 1970 Germany P 20 14 307.1 57 ABSTRACT 52 s C]137 29 2 5 2 ME, 137/6254g A pneumatic two-position controller in whichthe con- 51 1m. (:1. F156 3/04 Point is adjusted p i lly by means of apres- [58] Field 61 Search l37/625.48, 81.5, We distributor fletworkconnected between one 137/6255, 62549; 235/201 ME put of a differentialpressure amplifier and a source of auxiliary pressure, the pressuredistributor network [56] References cu providing the control pointpressure to one input of the UNITED STATES PATENTS differential pressureamplifier.

3,384,122 5/1968 Harpman l37/625.64 16 Claims, 3 Drawing FiguresPNEUMATIC TWO-POSITION CONTROLLER This invention relates to a pneumatictwo-position controller, the control points of which can be adjustedpneumatically.

Two-position controllers generally are control devices capable oftriggering switching processes when a variable is above and below thecontrol point, which switching processes, for example, open and close avalve. Conventional devices of this type start, for example, with ameasuring element (manometer, Bourdon spring, etc.) to which thevariable is fed and which produces a deflection proportional to thevalue of this variable. This deflection is transferred to a controlflapper, which operates, pneumatically or mechanically, two scanningdevices. Thus, for example, in a conventional system, the controlflapper interrupts the air stream between a jet nozzle and a collectingnozzle of a scanning device, the position of which is adjustable. Theseknown two-position controllers are complicated, and therefore require aconsiderable amount of space.

It is the object of this invention to provide a pneumatic two-positioncontroller which is simple to manufacture and operate and constitutes acompact design with a small number of structural parts.

The invention resides in providing a differential pressure amplifierhaving two input pressure chambers defined by elastic walls, one ofwhich chambers is supplied with a pressure equal to the value to becontrolled, whereas the second chamber is under the effect of a pressurevalue derived from a control point pressure distributor, the latterbeing fed by the output pressure of the differential amplifier and by anauxiliary pressure P Due to this design, many of the mechanical partsrequired in conventional devices, such as scanning heads, controlflappers, rotatable scanners, or the like, are eliminated. Therefore,the required amount of space occupied by the device of the presentinvention is very small. Also, the susceptibility of the device totrouble is minor.

In a further development of the invention, the provision is made toderive the auxiliary pressure P likewise from a pressure distributorwhich is fed, just like the amplifier, by the inlet or supply airpressure P,. This eliminates the need to provide a pressure generatorfor the control point pressure distributor.

It is advantageous, according to this invention, to utilize adifferential pressure amplifier producing two output pressures A and Awhich change simultaneously, but in the opposite sense, in dependence onthe difference between two input pressures P, and x applied thereto. Thepressure distributor, which serves to set the control points p,,, (uppercontrol point) and p, (lower control point), is alternately fed by theoutput pressures A and A. The ratio of the fluid throttle resistances ofthe pressure distributor determines the magnitude of the controlpressures P and P,,,. In this arrangement, they are symmetrical to A /2A/2 P l2.

In order to eliminate this symmetry of the control points to the outputpressures, the provision is made, according to the invention, to utilizea further pressure distributor fed by only one of the output pressures Aor A. The control point pressure distributor, in this embodiment, is feddirectly by one of the two output pressures, which is supplied to theamplifier indirectly via this pressure distributor.

These and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings,wherein:

FIG. 1 is a schematic circuit diagram of a twoposition controllerforming one embodiment according to this invention, the control pointpressure distributor of which is fed by one output of the differentialpressure amplifier and by an adjustable auxiliary pressure FIG. 2 is aschematic circuit diagram of a second embodiment, the control pressuresof which are formed by one or two pressure distributors fed by theoutput pressures A? and A' of the amplifier; and

FIG. 3 shows a particularly advantageous embodiment of a differentialpressure amplifier controlled in accordance with the present invention.

FIG. 1 shows a differential pressure amplifier l, the output pressures Aand A of which are proportional to the difference between the inputpressure signals x (variable) and P, The pressure A denotes the outputsignal which likewise increases with a rising input pressure x.Consequently, the pressure A increases with an increasing P, (controlpressure) and drops with an increasing pressure x. The differentialpressure amplifier is also fed by the amplification pressure P,.

Between the fluid throttle resistors 2 and 3 of the control pointpressure distributor, the control point pressure P, is derived andsupplied to the second input pressure chamber of the differentialamplifier l. The fluid resistor 3 of the pressure distributor hassupplied thereto the pressure A output; and, the adjustable fluidthrottle resistor 2 is fed by an adjustable auxiliary pressure P frompressure reducer 4. The value of the control point P, is determined bythe ratio of the fluid throttle resistors 2 and 3 and by the values ofthe pressures A and P supplied to the pressure distributor. For example,if x reaches the value of P,,,, then A has assumed the maximum value,wherein A" max P The following equation applies to P wherein A is theratio of the fluid throttle resistors 2 and 3 of the pressuredistributor.

Once x has reached the value x,,,, or has exceeded this value, theamplifier is actuated and pressure A drops to atmospheric pressure P,,.Then, the pressure P is present between the pressure distributor whichnow has P fed thereto, in accordance with the relationship:

In both relationships, A and P can be adjusted independently of eachother, so that P,,, and P also can be set independently of each other.

In place of the pressure reducer 4, required for adjusting the auxiliarypressure P it is also possible, as shown in dashed lines in FIG. I, toprovide a further pressure distributor made up of the fluid throttleresistors 5 and 6, fed just like the amplifier l by the inlet airpressure P,. In this case, the auxiliary pressure P is determined by theratio of the fluid throttle resistors S and 6, of which at least one isvariable, such as resistor S. In the embodiment of FIG. 1, it is notnecessary for the differential pressure amplifier to produce the twooutput pressures A and .4, since only one output pressure is utilized.

The embodiment of PK]. 2, in contrast to that of FIG. 1, is based on adifferential pressure amplifier 1 producing two output pressures A andA", both of which are utilized. The control point pressure distributor,consisting of the fluid throttle resistors 2 and 3, is connected betweenthe two output pressures A and A.

For x P, A P A'max, and A o so that the following equation applies:

Once x has reached the value x,,,, the amplifier is actuated, andpressure A assumes the value A min P 0, whereas pressure A increases toP The control' pressure assumes the value According to FIG. 3, a simpleconstruction of a differential pressure amplifier l is provided, as hasbeen described in German Patent Application No. P 19 55 083.5- l3, whichamplifier may be utilized in the embodiments of the inventionillustrated in FIGS. 1 and 2. This amplifier has two balls 9 ofidentical diameter which are displaceably arranged in a bore 10 of thehousing, and at least two channels 11 terminating in this housing bore,wherein the distance between the channels 11, as measured from onecenter to the other, corresponds to the diameter of the balls. Thespacing of the feed channel (P,) from one of the channels 11 is asmeasured from one center to the other approximately one-half thediameter of the balls 9.

While I have shown and described several embodiments in accordance withthe present invention, it is understood that the same is not limitedthereto but is susceptible of numerous changes and modifications asknown to a person skilled in the art, and I therefore do not wish to belimited to the details shown and described herein but intend to coverall such changes and modifications as are obvious to one of ordinaryskill in the art.

What is claimed is:

l. A pneumatic two-position controller comprising:

a differential pressure amplifier having first and second input pressurechambers defined by elastic walls, said first chamber being suppliedwith a first pressure to be controlled, said second chamber beingsupplied with a second control point pressure, and said amplifierproviding at least one output resulting from control of an inputpressure by said first and second pressures and proportional to thedifference between said first and second pressures, and

pressure distributor means for providing said second pressure to saidamplifier in response to at least one of said amplifier outputs.

2. A pneumatic two-position controller as defined in claim 1, whereinsaid pressure distributor means includes pressure divider means forproviding only a portion of'one of said amplifier outputs to saidamplifier.

3. A pneumatic two-position controller as defined in claim ll, whereinsaid pressure distributor means includes a pair of fluid throttleresistors connected in series between one output of said amplifier andan auxiliary pressure source, said second pressure supplied to saidsecond chamber of the differential pressure amplifier being derived froma point between said resistors.

4. A pneumatic two-position controller as defined in claim 3, whereinone of said resistors is variable.

5. A pneumatic two-position controller as defined in claim 3, whereinsaid auxiliary pressure source includes an additional pressuredistributor means connected to said input pressure supplied to saidamplifier.

6. A pneumatic two-position controller as defined in claim 3, whereinsaid pressure distributor means is connected at one end to said oneoutput of said amplifier through additional pressure distributor meansincluding an additional pair of fluid throttle resistors connected inseries to said one output, said pressure distributor means beingconnected to a point between said additional pair of resistors.

7. A pneumatic two-position controller as defined in claim 6, whereinone of said additional pair of fluid throttle resistors is variable.

8. A pneumatic twoposition controller as defined in claim 6, whereinsaid amplifier provides first and second reciprocally varying outputsresponsive to said input pressure controlled by said first and secondpressures applied to said first and second chambers, respectively.

9. A pneumatic two-position controller as defined in claim 8, whereinthe other end of said pressure distributor means is connected to theother output of said amplifier.

10. A pneumatic two-position controller as defined in claim 9, whereinone of said additional pair of fluid throttle resistors is variable.

11. A pneumatic two-position controller as defined in claim 1, whereinsaid differential amplifier includes first and second balls of identicaldiameter displaceably arranged in the bore of a housing, said ballsbeing operatively connected to the elastic wall of a respective one ofsaid first and second input pressure chambers so as to be displaced bymovement thereof, said housing being provided with a pair of outputbores spaced by the diameter of the balls and in alignment so as to bevalved by said balls and an input bore providing said input pressure tosaid balls for application to said output bores in a controlled manner.

12. A pneumatic two-position controller as defined in claim 11, whereinsaid pressure distributor means includes a pair of fluid throttleresistors connected in series between one output of said amplifier andan auxiliary pressure source, said second pressure supplied to saidsecond chamber of the differential pressure amplifier being derived froma point between said resistors.

13. A pneumatic two-position controller as defined in claim 12, whereinsaid auxiliary pressure source includes an additional pressuredistributor means connected to said input pressure supplied to saidinput pressure supplied to said amplifier.

14. A pneumatic two-position controller as defined in claim 13, whereinsaid pressure distributor means is connected at one end to said oneoutput of said amplifier through additional pressure distributor meansin- 6 plifier.

16. A pneumatic two-position controller as defined in claim 15, whereinone fluid throttle resistor in said pressure distributor means and insaid additional pressure distributor means is variable.

1. A pneumatic two-position controller comprising: a differentialpressure amplifier having first and second input pressure chambersdefined by elastic walls, said first chamber being supplied with a firstpressure to be controlled, said second chamber being supplied with asecond control point pressure, and said amplifier providing at least oneoutput resulting from control of an input pressure by said first andsecond pressures and proportional to the difference between said firstand second pressures, and pressure distributor means for providing saidsecond pressure to said amplifier in response to at least one of saidamplifier outputs.
 2. A pneumatic two-position controller as defined inclaim 1, wherein said pressure distributor means includes pressuredivider means for providing only a portion of one of said amplifieroutputs to said amplifier.
 3. A pneumatic two-position controller asdefined in claim 1, wherein said pressure distributor means includes apair of fluid throttle resistors connected in series between one outputof said amplifier and an auxiliary pressure source, said second pressuresupplied to said second chamber of the differential pressure amplifierbeing derived from a point between said resistors.
 4. A pneumatictwo-position controller as defined in claim 3, wherein one of saidresistors is variable.
 5. A pneumatic two-position controller as definedin claim 3, wherein said auxiliary pressure source includes anadditional pressure distributor means connected to said input pressuresupplied to said amplifier.
 6. A pneumatic two-position controller asdefined in claim 3, wherein said pressure distributor means is connectedat one end to said one output of said amplifier through additionalpressure distributor means including an additional pair of fluidthrottle resistors connected in series to said one output, said pressuredistributor means being connected to a point between said additionalpair of resistors.
 7. A pneumatic two-position controller as defined inclaim 6, wherein one of said additional pair of fluid throttle resistorsis variable.
 8. A pneumatic two-position controller as defined in claim6, wherein said amplifier provides first and second reciprocally varyingoutputs responsive to said input pressure controlled by said first andsecond pressures applied to said first and second chambers,respectively.
 9. A pneumatic two-position controller as defined in claim8, wherein the other end of said pressure distributor means is connectedto the other output of said amplifier.
 10. A pneumatic two-positioncontroller as defined in claim 9, wherein one of said additional pair offluid throttle resistors is variable.
 11. A pneumatic two-positioncontroller as defined in claim 1, wherein said differential amplifierincludes first and second balls of identical diameter displaceablyarranged in the bore of a housing, said balls being operativelyconnected to the elastic wall of a respective one of said first andsecond input pressure chambers so as to be displaced by movementthereof, said housing being provided with a pair of output bores spacedby the diameter of the balls and in alignment so as to be valved by saidballs and an input bore providing said input pressure to said balls forapplication to said output bores in a controlled manner.
 12. A pneumatictwo-position controller as defined in claim 11, wherein said pressuredistributor means includes a pair of fluid throttle resistors connectedin series between one output of said amplifier and an auxiliary pressuresource, said second pressure supplied to said second chamber of thedifferential pressure amplifier being derived from a point between saidresistors.
 13. A pneumatic two-position controller as defined in claim12, wherein said auxiliary pressure source includes an additionalpressure distributor means connected to said input pressure supplied tosaid input pressure supplied to said amplifier.
 14. A pneumatictwo-position controller as defined in claim 13, wherein said pressuredistributor means is connected at one end to said one output of saidamplifier through additional pressure distributor means including anadditional pair of fluid throttle resistors connected in series to saidone output, said pressure distributor means being connected to a pointbetween said additional pair of resistors.
 15. A pneumatic two-positioncontroller as defined in claim 14, wherein the other end of saidpressure distributor means is connected to the other output of saidamplifier.
 16. A pneumatic two-position controller as defined in cLaim15, wherein one fluid throttle resistor in said pressure distributormeans and in said additional pressure distributor means is variable.